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My name is Michelle Boychuk and I work for the North Peace Applied Research Association. I was wondering if you could help me answer a question. Do you know of any research being done showing that harvesting herbs at night is better than harvesting them in the morning?

I am not aware of any research that addresses your question specifically but I do know that Seija Haliva has done research on optimizing harvesting of herbs and may be able to help. Dr. Haliva lectured at the International Herb Association’s annual conference a few years ago summarizing what is known about optimizing harvesting times and conditions. You can read more on the web at http://www.iherb.org/articles/herbprod.html. Dr. Haliva’s book "Manual for Northern Herb Growers" written with Lyle Craker of the University of Massachusetts has references on the research in the cultivation of herbs including harvesting. The book is available from Richters.

There is anecdotal and folkloric indication that night time or early morning harvesting may be better than day time harvesting in some cases. Roots, for example, may best be harvested when transpiration is at a low at night because that’s when the plant’s "energies and properties" are said to move downward to the root. Here is a sample passage:

"The first light frosts is the signal for plants to start storing up their energies and properties into their roots to help them survive the long winter months. And so, it is the signal for us to go out and start digging. Ideally we are looking at the waning lunar phase. This is the time the lunar energy is pushing inward/downwards. And dig early in the morning, or if possible in the night, as the chilly night air tells the plant to send its energies and properties downward into the roots. Even this time of year we can have warm days, when the energies rise into the upper parts of the plant." [From: "Herb Root Harvesting in the Garden" by Stephanie Burgess, http://altnature.com/library/harvest.htm]

It is interesting to note that the practice of harvesting roots goes back to at least medieval times. Here’s a passage about harvesting mandrake roots (Mandragora officinarum):

"Medieval witches were said to harvest the root at night beneath gallows trees -- trees where unrepentant criminals, evil since birth, were supposed to have died. The root purportedly sprang up from the criminal’s body drippings. [From www.emandrake.org/History/history.html]

According to conventional wisdom the above ground parts of herbs are best harvested on sunny mornings soon after the dew has disappeared. That the dew must be gone before harvesting is easy to understand because the additional moisture on dew-laden herbs would slow the drying process and could potentially lead to the growth of moulds. Waiting until the sun has been up and transpiration rates are high may also help to speed drying because transpiring herbs have lower water content than fully hydrated herbs at night.

At least one herb enthusiast finds that basil is more fragrant early in the day or at night. As David Perry writes in the Culinary Herb FAQ maintained by Henrietta Kress (http://www.ibiblio.org/herbmed/faqs/culi-2-1-basil.html), "most of us don’t use basil at 3 a.m." implying that if we did we would find basil is better at that time. We have not tested this ourselves.